Fixed homebrew instructions.
Fixed homebrew instructions.

These have been wrong since
Homebrew/homebrew@da3eba7a97e3ac7207aa54f1b2e8c1a16c5378b7.

mbrukman/gcsfuse,jacobsa/timeutil,GoogleCloudPlatform/gcsfuse,BanzaiMan/gcsfuse,GoogleCloudPlatform/gcsfuse,BanzaiMan/gcsfuse,kahing/gcsfuse,GoogleCloudPlatform/gcsfuse,jacobsa/ratelimit